De Blasio told CNN’s “New Day” that Rahami, who is of Afghan descent, is a naturalized U.S. citizen. The FBI was searching a building at Rahami’s last known address in Elizabeth, New Jersey, on Monday.

“They will be there for the next few hours, going through this location to find any evidence possible, whether it’s in relation to this incident or the Chelsea incident,” Elizabeth Mayor Christian Bollwage told CNN.

An emergency alert was sent to cellphone users in the New York City area, telling residents to “Call 9-1-1 if seen.”

New York Gov. Andrew Cuomo (D) said the Chelsea bombing “was clearly an act of terrorism,” and said it’s possible there was “a foreign connection to the act.” As of Monday morning, no global terrorist groups have claimed responsibility for the blast.

“A bomb going off is, generically, linked to terrorist activity. And that’s how we’re going to prosecute it,” Cuomo said Sunday, speaking from the site of the blast.

Several people were reportedly taken into custody late Sunday in connection with the explosion. New York state Sen. Marty Golden (R) wrote on Instagram “the FBI took several individuals into custody on the Belt Parkway in the area underneath the Verrazano Bridge.”

The city was under heightened security and an increased police presence following the explosion, which prompted an investigation into a potential terror link, officials said.

Handout/Reuters
An image of Ahmad Khan Rahami, who is wanted for questioning in connection with an explosion in New York City, is seen in a a poster released by the FBI on Monday.

“I want New Yorkers to be confident when they go back to work Monday that New York is up and running and that we’re doing everything we need to do,” de Blasio said Sunday.

The city was already planning to increase police presence as foreign dignitaries arrive for the United Nations General Assembly meeting this week; after Saturday night’s explosion, residents and visitors should expect a “bigger than ever” presence, de Blasio said. Canines and heavy weapons teams have been assigned to transit hubs and stations, said Police Chief of Department Carlos Gomez.

An additional 1,000 New York State Police and National Guard officers have also been deployed to subway stations, Cuomo said Sunday.

The explosive device went off on 23rd Street between Sixth and Seventh Avenues Saturday evening, an area of the city that is teeming with nightlife on the weekends. A second device was found near the blast site and sent to the FBI’s lab in Quantico for analysis, Sgt. Brendan Ryan told The Huffington Post.

Cuomo said the incident could be related an explosion in New Jersey earlier on Saturday, when one pipe bomb exploded and two more were recovered along the route of a 5K charity race, authorities said. Authorities said a July incident in which a pipe bomb injured a tourist in New York’s Central Park was not related.

Security cameras in a nearby buildings captured the blast which happened shortly after 8 p.m.:

Officers responded to reports of a second explosive device nearby, on 27th Street between Sixth and Seventh Avenues, just before 11 p.m. Police recovered a bag with a pressure cooker connected to wires and a cell phone, NBC News and NY1 reported.

Cuomo said the second device was “similar in design” to the one that blew up on 23rd Street; he said the multi-part explosive recovered in New Jersey was different. But on Monday, Cuomo said “there are similarities” in the New York and New Jersey devices.

“They are not identical, but there are certain similarities in the way the bombs were put together with certain elements, et cetera, suggesting that there might have been a common linkage or a common person behind all the bombs,” Cuomo told CNN.

The Huffington Post
An explosion (below) went off in Chelsea Saturday evening; police found a possible explosive device four blocks north of the blast site (above).

Cuomo said Sunday that there were no fatalities and that all of the injured had been released from the hospital. He noted that at least 1,000 extra officers and the National Guard had been mobilized to monitor the city’s subway system.

Visitors crowded the barricades that police used to block off the area, which is a popular nightlife destination. Many onlookers were stranded tourists, who were unable to return to their hotels.

RASHID ABBASI / Reuters
Onlookers stand behind a police cordon near the site of the explosion in the Chelsea neighborhood of Manhattan, New York City, on Saturday night.

President Barack Obama was due to travel to New York City on Sunday ahead of a United Nations General Assembly session, scheduled to begin Monday.

Chelsea, a largely residential neighborhood on the west side of Manhattan, is a popular nightlife destination and is usually bustling on weekends. The intersection near the site of the explosion, Sixth Avenue and 23rd Street, is one of several train hubs in the area, just south of Madison Square Garden and north of Chelsea Market and Google’s corporate campus, and 23rd street is also a busy thoroughfare for crosstown traffic.

Cat Hess had her windows “wide open” on 22nd Street, between Seventh and Eighth Avenues, when she heard the explosion.

“You know when large trucks hit steel plates in the street? It was super loud, like a semi hitting steel plates,” she told HuffPost.

thekdish/Instagram

Javier Quintans, 33, a general manager at Francisco’s Centro Vasco, near Seventh Avenue and 23rd Street, said he thought something had fallen on the restaurant.

“We evacuated all the patrons and now we’re being told to stay indoors or leave the area,” he told HuffPost Saturday night.

RASHID ABBASI / Reuters
Police use a dog to search the site of an explosion in the Chelsea neighborhood of Manhattan, New York City, on Saturday.

Republican presidential nominee Donald Trump told supporters at a Colorado rally that a bomb had gone off in New York City, despite no officials stating that this had happened.

“Just before I got off the plane, a bomb went off in New York and nobody knows exactly what’s going on,” Trump said. “We better get very tough.”

After receiving criticism for calling the incident a bombing before facts were known, Trump bragged Monday that what he said was “exactly correct.”

“I should be a newscaster because I called it before the news,” Trump told Fox News.

Though Democratic presidential candidate Hillary Clinton initially described the blasts in New York City and New Jersey as bombings, she later said “it’s important to know the facts” before citing the cause of a such incidents.

“I think it’s always wiser to wait until you have information before making conclusions,” she said, in response to Trump’s comments.

Carina Kolodny, Paige Lavender, Christopher Mathias, Lydia O’Connor, Meg Robertson and Victor Brand contributed reporting. This post has been updated with the name of one suspect.